Summary of Investments - SOI Fixed Maturity AFS aging (Details 2) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Amortized cost
Maturing in one year or less	$ 644,280
Maturing after one year through five years	3,845,273
Maturing after five years through ten years	6,950,269
Maturing after ten years	5,073,643
Mortgage-backed and asset-backed securities	4,914,337
Amortized cost	21,427,802	$ 21,672,727
Estimated fair value
Maturing in one year or less	662,742
Maturing after one year through five years	4,018,406
Maturing after five years through ten years	7,068,702
Maturing after ten years	5,282,788
Mortgage-backed and asset-backed securities	5,009,698
Estimated fair value	$ 22,042,336	$ 22,153,703